Proximity service (ProSe) refers to a scheme for supporting communication between devices located physically close to each other. Specifically, ProSe is aimed to discover an application operating devices which are in proximity and, ultimately, to support exchange of data related to the application. For example, it may be considered that ProSe is applied to applications such as social network services (SNS), commerce, and games.
ProSe may be also called device-to-device (D2D) communication. That is, ProSe refers to a communication scheme for establishing a direct link between a plurality of devices (e.g., user equipments (UEs)) and thus directly exchanging user data (e.g., audio, multimedia data, etc.) between the devices without going via a network. ProSe communication may include UE-to-UE communication, Peer-to-Peer communication, etc. In addition, ProSe communication may be applied to Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), etc. Accordingly, ProSe is considered as one solution to reduce the burden of a base station due to rapidly increasing data traffic. Besides, by adopting ProSe, effects such as reduction in procedures of a base station, reduction in power consumption of devices which participate in ProSe, increase in data transmission speed, increase in network capacity, load distribution, cell coverage expansion, etc. can be expected.